Buildworld can't find platform.h anymore

In file included from /usr/src/lib/libisc/../../contrib/bind-9.2.4rc4/lib/lwres/lwinetntop.c:29:
/usr/src/lib/libisc/../../contrib/bind-9.2.4rc4/lib/lwres/unix/include/lwres/net.h:53:65: lwres/platform.h: No such file or directory
mkdep: compile failed